Noninvasive prenatal testing (NIPT) to detect fetal aneuploidy (an abnormal number of chromosomes) using massive parallel sequencing of cell-free DNA (cfDNA) from maternal blood is gaining rapid acceptance in obstetrics, given its high sensitivity and specificity for the detection of trisomies 21, 18, and 13. Placental DNA, a surrogate of fetal DNA, enters the maternal bloodstream via apoptosis of trophoblasts in the intervillous space of the placenta, where it mixes with cfDNA of maternal origin. The fetal fraction in this mixture usually varies between 3% and 15% in the late first and second trimesters. NIPT represents a form of advanced screening, and positive results consistent with aneuploidy require confirmation by a diagnostic test using material obtained via amniocentesis or chorionic villus sampling (CVS).1,2
Romero R, Mahoney MJ. Noninvasive Prenatal Testing and Detection of Maternal Cancer. JAMA. 2015;314(2):131–133. doi:10.1001/jama.2015.7523
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